SIMMS and other memory dongles

Eric J Korpela korpela at
Sat Feb 11 01:32:06 CST 2006

Wow, January 31.  Due to the talk-to-tech delay, this might have been
answered already, but here goes...

> Is there an easy way to spot the size of the SIMM?  I don't have chip
> numbers memorized.

For 72 pin SIMMS, the installed jumper (0 ohm) resistors usually tell
the story on size and speed.

The key I have says jumpers J1 and J2 are the size.  J3 and J4 are the speed.

..00   60ns
..10   70ns
..01   80ns
..11   50 or 100ns.

00..   8MB
10..   1MB or 16MB
01..   2MB or 32MB
11..   4MB or 64MB

If there are only two jumpers on your SIMM it's probably a 60ns SIMM. 
You can usually guess whether it's parity or not by chip count.

If pin 19 is connected, it's probably the larger of the two options. 
I don't know how to identify smaller SIMMS (128K and 512K 72-pin SIMMS
apparently existed, Maybe J0 and J5 which are identified in some data
sheets, but I've never seen a SIMM with jumpers for them.)

For 30 pin SIMMS you'll probably need to look at the chips.  Most of
the time there's an obvious sign of the size (a 256 or 512 in the part

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